The invention refers to the field of reproduction technology and is directed to a device for dividing a light beam into two sub-beams which comprises a polarization beam splitter having a polarizing layer.
Such a device for beam division can be employed, for example, in a light beam scanner means for originals scanners or for recording devices.
In an originals scanner, also referred to as an input scanner, the light beam is conducted point-by-point and line-by-line across the original to be scanned, and the scan light reflected by the original or allowed to pass by the original is converted into an image signal in an opto-electronic converter. In a recording device, also referred to as a recorder, exposer or output scanner, the light beam is intensity-modulated by an image signal for recording information and is guided point-by-point and line-by-line across a light-sensitive recording medium.
In the case of a flat-bed device, the holder for the original or, for the recording medium, is a planar surface over which the light beam is guided point-by-point and line-by-line and that moves relative to the light beam scanner means.
In the case of an inside drum device, the holder for the original or, the recording medium is designed as a stationary half-shell or trough. The light beam scanner means moves parallel to the longitudinal axis of the half-shell or trough, and the light beam is radially guided over the original or, the recording medium perpendicularly relative to the longitudinal axis.
For example, EP-A-0 354 028, corresponding to U.S. Pat. No. 5,011,245 which discloses an inside drum exposer, discloses a means for beam division. With the device recited therein, it is possible to align the sub-beams such that they have an offset of approximately 180.degree.. Upon rotation of the device in the inside drum, a double beam deflection can be thereby achieved in order to increase the recording speed.
Another device for beam division having a polarization beam splitter wherein a prism is employed as a carrier for the polarizing layer is disclosed by DE-C-39 18 075. The combination of reflection and refraction properties makes it possible to deflect a light beam into a prescribed direction with the assistance of the prism.
EP-B-0 126 469 corresponding to U.S. Pat. No. 4,595,957, discloses that the deflection of light beams over an inside drum be implemented with a rotating mirror. It is possible to illuminate a useful region of 120.degree. with the assistance of the mirror.
Another device for beam deflection in inside drum exposers is disclosed by WO 90/15 355 corresponding to U.S. Pat. No. 4,936,643. In order to avoid the influences of disturbances, two reflection faces are arranged at a rotating shaft here, the one, first reflection face thereof facing toward a radiation source steering the light emission in the direction onto the second reflection face and the latter aligning the light beam onto a material to be exposed.
U.S. Pat. No. 4,878,720 discloses various prism shapes that, however, lead to long running paths of the light beam within the prism and therefore require extremely high-grade and pure glasses in order to avoid deteriorations of the transmission quality.
The known devices do not make it possible to realize a beam splitter such that it is both constructed in a structurally simple way and also guarantees a qualitatively high-grade beam transmission.